In the past, the majority of refrigerator/freezer lighting systems incorporated incandescent lamps. Incandescent lamps heat up the interior of the refrigerator thereby decreasing the efficiency, and also have to be replaced frequently.
In my U.S. Pat. No. 6,034,485, I disclose lighting systems in which high-frequency, ballast-free, square-wave drivers are utilized to non-thermionically initiate and maintain discharges in lighting systems. In my application Ser. No. 08/942,670, filed Oct. 2, 1997, I disclose fluorescent lighting systems which use my ballast-free, non-thermionic high-frequency AC square-wave driver system which start and operate fluorescent lamps without significant change in voltage. These non-thermionic driver systems do not use heated filaments, and, surprisingly, it has been found that they are efficient in starting and operating in cold temperatures and provides more efficient cold environment lighting systems.
The present invention adapts the non-thermionic high-frequency (40 kHz to 120 kHz) alternating current drivers to start and operate lighting systems for cold environments such as refrigerator/freezers, walk-in coolers, cold food display cases, etc.
The invention provides a cold environment fluorescent lamp lighting system for refrigerators, freezers, display cases, walk-in coolers, etc. comprising a circuit for generating a high-frequency (40 kHz-120 kHz) alternating current voltage waveform, and a circuit for non-thermionically applying in a ballast-free manner the high-frequency alternating current voltage waveform to lamp electrodes to start and operate the lamp(s). The high-frequency alternating current voltage waveform as applied to the lamp electrodes is configured to reverse the polarity of the alternating current voltage at the lamp electrodes more rapidly than the pattern of electron and ion density in the gaseous medium can shift.
Thus, the object of the invention is to provide an improved cold environment lighting systems.